This invention relates to cryogenic apparatus for cooling objects to and maintaining them at a very low temperature in which by the use of the confinement produced by the thermomechanical effect superfluid helium II is evaporated from a supply container through a throttle element having a narrow passage into an evacuable system.
The use of superfluid helium II for the cooling of objects to a temperature below 2.degree. K. is known for terrestrial and extra-terrestrial purposes, for example, in connection with radiation detectors.